Positive resist composition and pattern forming method using the same

1. A positive resist composition comprising:

(A) a resin containing a repeating unit represented by formula (I), which is insoluble or hardly soluble in an alkali developer and becomes soluble in an alkali developer under the action of an acid;

(B) a compound capable of generating an acid upon irradiation with actinic rays or radiation; and

(C) an organic basic compound:

wherein R 1 represents a hydrogen atom, a methyl group, a cyano group, a halogen atom or a perfluoro group,

R 2 represents a non-acid-decomposable group containing an oxygen atom,

X represents a hydrogen atom or an organic group,

m represents an integer of 1 to 4,

n represents an integer of 1 to 4, provided that 2≦n+m≦5,

when m is an integer of 2 to 4, multiple Xs may be the same or different, and

when n is an integer of 2 to 4, multiple R 2 s may be the same or different.

2. The positive resist composition as claimed in claim 1 , wherein the repeating unit represented by formula (I) is a repeating unit represented by formula (Ia):

wherein R 1 represents a hydrogen atom, a methyl group, a cyano group, a halogen atom or a perfluoro group,

R 2 represents a non-acid-decomposable group,

X represents a hydrogen atom or an organic group,

n represents an integer of 1 to 4, and when n is an integer of 2 to 4, multiple R 2 s may be the same or different.

3. The positive resist composition as claimed in claim 1 , wherein the repeating unit represented by formula (I) is a repeating unit represented by formula (Ib):

wherein R 1 represents a hydrogen atom, a methyl group, a cyano group, a halogen atom or a perfluoro group,

X represents a hydrogen atom or an organic group, and

R 2a and R 2b each independently represents a hydrogen atom or a non-acid-decomposable group, provided that at least one of R 2a and R 2b is a non-acid-decomposable group.

4. The positive resist composition as claimed in claim 1 , wherein the non-acid-decomposable group of R 2 in formula (I) is an alkoxy group.

5. The positive resist composition as claimed in claim 1 , wherein the resin (A) further contains a repeating unit represented by formula (II):

wherein R 3 to R 5 each independently represents a hydrogen atom, a fluorine atom, a chlorine atom, a cyano group or an alkyl group, and

X 1 represents a hydrogen atom or an organic group.

6. The positive resist composition as claimed in claim 5 , wherein a group of X 1 in formula (II) contains at least one of an alicyclic structure and an aromatic ring structure.

7. The positive resist composition as claimed in claim 1 , which further comprises (D) a surfactant.

8. The positive resist composition as claimed in claim 1 , wherein the component (B) includes (B1) a compound capable of generating an organic sulfonic acid under the action of actinic rays or radiation.

9. The positive resist composition as claimed in claim 8 , wherein the component (B) further includes (B2) a compound capable of generating a carboxylic acid under the action of actinic rays or radiation.

10. The positive resist composition as claimed in claim 1 , which further comprises a solvent.

11. The positive resist composition as claimed in claim 10 , wherein the solvent contains propylene glycol monomethyl ether acetate.

12. The positive resist composition as claimed in claim 11 , wherein the solvent further contains propylene glycol monomethyl ether.

13. The positive resist composition as claimed in claim 1 , which is for an exposure by the irradiation of electron beam, X-ray or EUV.

14. A pattern forming method comprising: forming a resist film by using the positive resist composition claimed in claim 1 ; and exposing and developing said resist film.